Glandular breast dose for monoenergetic and high-energy X-ray beams: Monte Carlo assessment.

PURPOSE: To extend the utility of normalized glandular dose (DgN) calculations to higher x-ray energies (up to 120 keV) and to provide the tools for investigators to calculate DgN values for arbitrary mammographic and x-ray spectra. MATERIALS AND METHODS: Validated Monte Carlo methods were used to assess DgN values. One million x-ray photons (1-120 keV, in 1-keV increments) were input to a semicircular breast geometry of thicknesses from 2 to 12 cm and breast compositions from 0% to 100% glandular. DgN values for monoenergetic (1-120 keV) x-ray beams, polyenergetic (40-120 kV, tungsten anode) x-ray spectra, and polyenergetic mammographic spectra were computed. Skin thicknesses of 4-5 mm were used. RESULTS: The calculated DgN values were in agreement within approximately 1%-6% with previously published data, depending on breast composition. DgN tables were constructed for a variety of x-ray tube anode-filter combinations, including molybdenum anode-molybdenum filter, molybdenum anode-rhodium filter, rhodium anode-rhodium filter, tungsten anode-rhodium filter, tungsten anode-palladium filter, and tungsten anode-silver filter. DgN values also were graphed for monoenergetic beams to 120 keV and for general diagnostic x-ray beams to 120 kV. CONCLUSION: The tables and graphs may be useful for optimizing mammographic procedures. The higher energy data may be useful for investigations of the potential of dual-energy mammography or for calculation of dose in general diagnostic or computed tomographic procedures.     

Can tamoxifen cause a significant mammographic density change in breast parenchyma?

To evaluate tamoxifen-induced glandular tissue density changes in women who are on an adjuvant tamoxifen therapy. We examined serial mammograms of 27 women (average age 67) who had surgery for unilateral breast carcinoma and were on tamoxifen for 5 years. Mammograms obtained at the beginning of treatment, within 2 or 3 years, at the end of 5 years and 1 year after cessation of tamoxifen treatment, were evaluated by two radiologists experienced in reading mammograms. Four 1-cm-diameter circular areas of the glandular tissue and retroglandular fat were sampled by a densitometer and a relative glandular density (glandular tissue/fat density) was used for comparison between serial mammograms. Most cases (79%) did not show tamoxifen-induced change in glandular density. Three patients (13%) showed an early and two (8%) a delayed mild reduction in glandular density as compared to baseline mammograms. No patient was found to have increased glandular density following the cessation of tamoxifen therapy (in subjective evaluation). Densitometer readings showed a mild reduction in glandular densities in 16 cases (60%) during treatment and a minimal increase in 13 cases (48%) following cessation of treatment. There was a slight decrease in breast density during treatment [relative density of 0.012+/-0.006 (standard error) per interval, P value:.06] and the difference between years 5 and 6 was nearly zero [relative density of 0.00042+/-0.01 (standard error), P value:.97]. Long-term use of tamoxifen may cause a mild reduction in breast glandular density, although this, in part, may be attributed to the age-related mammographic density change. Following cessation of tamoxifen, no significant increase in glandular density was observed. Therefore, any increase in mammographic density during or after tamoxifen treatment should be viewed with suspicion and further evaluated.     

Dosage evaluation in mammography

Estimates of breast dose per view are needed for selection of mammographic techniques and verification of their proper use. However, accurate dosimetry requires standardization of both the methodology and the assumed breast composition. Because several different methods have been reported, the authors developed a simple and reproducible method using a reference "average breast" composition of 50/50% water/fat by weight. Working curves were derived for average glandular and whole-breast dose per unit of exposure in air vs. HVL and thickness. When these curves are combined with on-site measurements of exposure per view, one obtains values of dose per view for each technique. Factors were also computed to correct dosage from the reference composition to other breast compositions.     

Female breast radiation exposure during CT pulmonary angiography

OBJECTIVE: The objective of our study was to estimate the effective radiation dose to the female breast during CT pulmonary angiography compared with other routine diagnostic imaging techniques. MATERIALS AND METHODS: We retrospectively reviewed the demographic data of patients who underwent CT pulmonary angiography between May 2000 and December 2002, the diagnostic yield of those studies, and the estimated effective radiation dose to the breast incurred during CT. The estimated effective radiation dose was calculated using the ImPACT CT (Impact Performance Assessment of CT) dosimetry calculator and the CT dose index (CTDI) and was compared with the average glandular dose for two-view screening mammography. RESULTS: During the study period, 1,325 CT pulmonary angiograms were obtained. Sixty percent (797) of the scans were obtained on female patients. The mean age of scanned females was 52.5 years (range, 15-93 years). Of the studies performed in females, 401 (50.31%) were negative, 151 (18.95%) were nondiagnostic, and 245 (30.74%) were positive for pulmonary thromboembolism. The calculated effective minimum dose to the breast of an average 60-kg woman during CT was 2.0 rad (20 mGy) per breast compared with an average glandular dose of 0.300 rad (3 mGy) for standard two-view screening mammography. CONCLUSION: CT pulmonary angiography delivers a minimum radiation dose of 2.0 rad (20 mGy) to the breasts of an average-sized woman. This greatly exceeds the American College of Radiology recommendation of < or = 0.300 rad (3 mGy) or less for standard two-view mammography. The potential latent carcinogenic effects of such radiation exposure at this time remain unknown. We encourage the judicious use of CT pulmonary angiography and lower doses and nonionizing radiation alternatives when appropriate.     

Effect of breast composition on patient exposure in mammography

Software for the estimation of patient exposure from mammography has been developed. Because it adopts average glandular dose, the estimation of patient exposure must take advantage of D(gN) (average glandular dose per unit entrance skin exposure). D(gN) depends on X-ray quality, compressed breast thickness, and breast composition. The software that was previously reported required information about breast composition. However, the new software that estimates breast composition uses a phantom with known breast composition to estimate average glandular dose and entrance surface dose. The authors were able to calculate average glandular dose that takes account of breast composition using this software. In addition, in a comparison with the mammogram in terms of the classification of mammary gland substance, the software showed high precision in terms of agreement. This software has sufficient utility because only the mammographic conditions are entered, and patient exposure can be easily estimated. Moreover, the half-value layer, incident exposure in air, D(gN), and breast composition can be specifically calculated.     

Comparison between high-resolution helical CT and pathology in breast examination

Purpose:
To determine whether high-resolution helical CT can show the architectural features of breast carcinomas of non-limited extent (non-BCLE) and to establish the CT characteristic morphology of non-BCLE. Material and Methods:
We prospectively studied high-resolution helical CT of 136 invasive breast carcinomas before breast-conserving surgery. Non-BCLE were defined as ductal carcinomas in situ and invasive carcinomas beyond 1 cm from the edge of the dominant mass. Non-BCLE were defined as positive if enhanced beyond 1 cm from the edge of the focal enhancement on CT. After surgical resection, specimens were sliced in serial sections at 5-mm intervals, and the gross morphology and histology were correlated with the appearance of the preoperative CT lesion images. Results:
Non-BCLE were present in 47 invasive carcinomas. The sensitivity and specificity of non-BCLE evaluation by high-resolution helical CT were 70% and 89%, respectively. The morphology of non-BCLE on CT agreed with histologic findings. The morphological pattern on CT significantly correlated with intraductal tumor density adjacent to invasive tumor. Conclusion:
Comparison of high-resolution helical CT with histologic data suggests that demonstration of a non-BCLE morphology can make the CT breast carcinoma local staging more accurate.     

Female breast surface radiation exposure during FDG PET/CT examinations

BACKGROUND: The combined positron emission tomography (PET) and computed tomography (CT) scanners have been developed in which CT data can be used for both anatomical landmarks and attenuation correction of PET images. However, this modality potentially introduces more radiation burden to patients compared to conventional PET scanning as a result of the added radiation exposure received from CT examination. The purpose of our study was to determine the breast radiation doses of combined PET/CT examination. MATERIAL AND METHODS: Patients' superficial breast doses were calculated using thermoluminescence dosimeters (TLDs) placed onto the surface of the breasts. TLDs were positioned before FDG injection and removed after 24 h. We also determined the average superficial and glandular breast radiation doses from the anthropomorphic dosimetric phantom imaged using similar CT protocol (low dose) to the patients' study. RESULTS: The mean superficial breast dose of the breast skin measured from the PET/CT studies was 14.42+/-2.41 mGy. The average superficial and glandular breast doses of the anthropomorphic phantom measured from the low-dose CT was 9.50 mGy and 5.94 mGy, respectively. CONCLUSION: This study showed that radiation exposure to the breasts during PET/CT was higher than the recommended doses. Therefore, combined PET/CT scanning must be used for essential indications, particularly in women of reproductive age and preferentially a low-dose CT protocol should be implemented to avoid overexposure in such patients.     

How does semi-automated computer-derived CT measure of breast density compare with subjective assessments to assess mean glandular breast density,in patients with breast cancer?

Objectives:

(a) To compare radiologists'' breast mammographic density readings with CT subjective measures. (b) To correlate computer-derived measurement of CT density with subjective assessments. (c) To evaluate density distributions in this cohort of patients with breast cancer.

Methods:

A retrospective review of mammograms and CT scans in 77 patients with breast cancer obtained within 1 year of each other was performed. Two radiologists independently reviewed both CT and mammograms and classified each case into four categories as defined by the breast imaging-reporting and data system of the American College of Radiology. Inter-reader agreements were obtained for both mammographic and CT density subjective evaluations by using the Cohen-weighted kappa statistic and Spearman correlation. The semi-automated computer-derived measurement of breast density was correlated with visual measurements.

Results:

Inter-reader agreements were lower for subjective CT density grades than those for mammographic readings 0.428 [confidence interval (CI), 0.24–0.89] vs 0.571 (CI, 0.35–0.76). There was moderately good correlation between subjective CT density grades and the mammographic density grades for both readers (0.760 for Reader 1 and 0.913 for Reader 2). The semi-automated CT density measurement correlated well with the subjective assessments, with complete agreement of the density grades in 84.9% of patients and only one level difference in the rest.

Conclusions:

Semi-automated CT density measurements in the evaluation of breast density correlated well with subjective mammographic density measurement.

Advances in knowledge:

There is good correlation between CT and mammographic density, but further studies are needed on how to incorporate semi-automated CT breast density measurement in the risk stratification of patients.High glandular density on mammograms has been identified as a risk factor for development of breast cancer.^1–3 Moreover, mammograms of breasts with high glandular density have low sensitivity for diagnosing breast cancer. There has been an impetus to use methods other than traditional mammograms to evaluate breasts with high density such as ultrasound and MRI.^4,5On the other hand, CT scans are increasingly performed in a variety of age groups for reasons other than breast symptoms. Following recent recommendations of low-dose chest CT screening for lung cancer in high-risk patients,⁶ many females have had CT of the chest performed but not mammograms. We believe that CT provides a valuable resource to get reliable information with respect to breast density. If breast density can be determined accurately and is deemed to be high on CT scan, there is a case to suggest supplemental screening with other modalities in addition to mammography.The aim of this study is to evaluate (1) if semi-automated CT measurement of density is a reliable method to measure breast density by comparing computer-generated values with visual mammographic density values and subjective CT measurements and (2) to evaluate the density distribution in this cohort of breast cancers.     

腋部副乳腺的X线诊断

目的 认识腋部副乳腺的X线表现。方法 回顾性复习了3年来的7562例女性接受日常乳腺X线检查的内侧斜位照片,观察有无副乳腺及其X线表现。诊断依据为：在腋内有和主乳腺不相连的腺体样结构。结果 7562例中发现腋部副乳腺161例,发生率2％,平均年龄39岁。38％发生于两侧,42％发生于右侧,20％发生于左侧。最大径线平均为3．5cm(右）和3．3cm(左）。在形态上,斑片状最多（35％）,其余依次为分支状（26％）、混合状（20％）及团片状（19％）。3例手术病理证实为乳腺组织。结论 腋部副乳腺不少见,有一定的X线表现,认识它很重要,以避免将此种发育异常误认为其他病变。     

Production design and evaluation of a novel breast phantom with various breast glandular fractions

The purpose of this study was to evaluate the production design of a novel breast phantom, which has adjustable breast glandular fractions and potential application in the mammography quality assurance/quality control system. The breast phantom was based on a urethane resin that was used to adjust the breast glandular fraction by varying the amount of plasticizer added. The resin was cured at constant temperature and humidity. Theoretical phantom properties, such as elemental composition, specific density, effective atomic number, electron density, and linear attenuation coefficients, at various energies were compared to those of breast tissue tabulated in the ICRU 44. These properties were also compared to polymethyl methacrylate resin and BR12. The novel breast phantom was made to represent breast glandular content calculated from breast tissue of the ICRU 44. We hypothesized that the breast phantom theoretical properties are approximately equal to those of the BR12, which is known for being an excellent substitute breast phantom. It was found that the phantom can be used to improve both mammography performance and dosimetry.     

Localization of breast lesions identified on only one mammographic view

Occasionally, a breast lesion is visible in only one mammographic projection. A simplified method of using parallax in a dedicated mammographic system has been devised to locate accurately lesions that are not visible in two orthogonal projections. In eight patients, a parallax approach from essentially a single mammographic position was used to place a hookwire preoperatively at nonpalpable suspicious abnormalities detected by mammography. Needles were inserted parallel to the chest wall while the breast was compressed in the mammographic unit. In each case, the tissue containing the lesion was pierced by a needle chosen to be longer than the distance from the skin to the abnormality. Simple geometric ratios were used to determine the position of the lesion along the needle shaft after slightly changing the mammographic projection and viewing the needle obliquely. In all cases, this parallax approach permitted accurate localization of the lesion.     

Statistical analysis of mammographic breast composition measurements: towards a quantitative measure of relative breast cancer risk

Objective

A number of studies have identified the relationship between the visual appearance of high breast density at mammography and an increased risk of breast cancer. With the advent of digital mammography and the promise of routine measurements of parameters associated with breast composition, the possibility arises of using breast composition in a quantitative manner to predict relative breast cancer risk. Previous measurements have shown that the average proportion of glandular and adipose tissue within the breast varies with both age and breast size. In order to be able to identify individual women with an unusually high volume of glandular tissue, it will therefore be necessary to make comparisons with a disease-free population matched for age and breast size.

Methods

A large number of breast glandular thickness measurements were analysed to investigate the statistics of breast composition across a disease-free population as a test of a suitable methodology for relative risk estimation. The large data set is also used to revisit the trends in breast composition used in the current UK method of breast radiation dosimetry.

Results

It is demonstrated that a non-linear transformation can be used to produce normal statistical distributions, suitable for producing a standardised “Z-score” for breast composition.

Conclusion

A standard “Z-score” approach to identify women with unusually glandular breasts is recommended and so provide a basis for cancer risk estimations.It is generally accepted that a link exists between so-called “breast density”, i.e. the proportion and pattern of bright areas in a mammographic image denoting glandular tissue, and the relative risk of breast cancer. The field has been reviewed by Harvey and Bovbjerg [1], who identified 12 studies in which quantitative methods of measuring breast density showed a moderate to strong positive association with breast cancer risk. The risk of breast cancer for women with increased breast density in most of these studies is four to six times that for women with primarily adipose breasts; a relative risk greater than most traditional risk factors such as nulliparity and early menarche. With the advent of digital mammography and the promise of replacing visual assessment of breast density with quantitative measurements of parameters associated with breast composition, the possibility arises of using breast composition to predict relative breast cancer risk. In this article, a large number of breast glandular thickness measurements are analysed to investigate the statistics of breast composition across a disease-free population as a test of a suitable methodology for relative risk estimation.Despite the structural and functional complexity of the female breast, in terms of its mammographic appearance, and for the purposes of constructing a simple cancer risk model, it is convenient to regard the breast as being composed of two tissue components, adipose and glandular. These two components can be defined in terms of their X-ray attenuation properties [2], and phantom materials mimicking their physical characteristics at the X-ray energies commonly employed in mammography are commercially available (CIRS, Norfolk, VA). Any method of calibration of mammographic radiographic units which aims to measure breast composition that employs these phantom materials will therefore be contributing to a convenient standardisation of the definition of the adipose and glandular components. A number of such methods has been described, and the quantities proposed as the risk-related measure have covered a considerable range, with some form of percentage glandularity a frequent suggestion for the risk-related variable [3–6].What is being described as glandular tissue here is in fact a combination of fibroglandular and connective tissue in which the proportion of luminal epithelium, from which most cancers arise, is known to be quite small [7]. However, if the basic assumption is made that an increased relative risk of breast cancer is associated with an unusually large number of glandular cells in the individual breast, that the number of cells at significant risk of carcinogenesis will be proportional to the volume of fibroglandular and connective tissue and that the relative risk associated with the volume of adipose tissue present is negligible, then it would seem reasonable to aim at quantifying the breast composition in terms of the volume of fibroglandular and connective tissue present [8]. With the advent of full-field digital mammography, such volumetric measurements are possible, although there is likely to be a number of competing approaches to the problem in the medium term. Even with the promise of reliable delivery of an estimate of the volume of glandular tissue with each digital mammogram in the future, the question still arises as to the best way of employing such information to measure relative risk of breast cancer and make decisions on patient management.     

Increased radiation dose at mammography due to prolonged exposure, delayed processing, and increased film darkening

Four single-emulsion films introduced over the past 2 years--Du Pont Microvision, Fuji MiMa, Konica CM, and Eastman Kodak OM--were compared with Eastman Kodak OM SO-177 (Min-RE) film to evaluate their varying effects on mean glandular dose of reciprocity law failure due to prolonged exposure, delayed processing, and increased film darkening as a result of increased radiation exposure to improve penetration of glandular tissue. Exposures over 1.3 seconds led to increased radiation doses of 20%-30%. Delays in processing of 6 hours decreased processing speed by 11%-32% for all films except Du Pont Microvision. Optical density increases of 0.40 required 20%-30% more skin exposure for all five films. Optimal viewing densities were also evaluated and found to be different for each of the five films. Mammographers need to be aware of these differences in mammographic films to achieve maximum contrast at mammography.     

乳腺癌的不典型X线表现

目的：探讨乳腺癌不典型的X线征象及诊断。方法：按照美国放射学会(ACR)创立并推荐的乳腺影像报道及数据系统的标准，总结分析27例经手术病理征实的乳腺癌不典型X线征象。结果：27例中，乳腺结构变形10例，肿块11例，钙化6例。结论：乳腺癌在X线征象上不具特征性，可表现为乳腺结构扭曲、局限致密、毛刺肿块、钙化。仔细阅片，全面分析，必要时行B超、CT、MRI、SCNB等影像学检查，可提高诊断准确率。     

Spectral dependence of glandular tissue dose in screen-film mammography

The average glandular tissue dose in mammography is generally determined from published tables with knowledge of the breast entrance skin exposure, x-ray tube target material, beam quality (half-value layer [HVL]), breast thickness, and breast composition. Using a carefully designed and experimentally validated Monte Carlo simulation, the authors found that average glandular dose also depends on x-ray tube voltage and, to a lesser extent, on x-ray tube voltage waveform. For currently employed molybdenum target-molybdenum filter source assemblies, a difference in dose of 10% or more is possible in estimating the average glandular dose obtained with different x-ray tube voltages but with the same HVL. Presented are normalized average glandular tissue doses in units of radiation absorbed dose per unit entrance skin exposure for different tube voltages and tube voltage waveforms as well as for different breast thicknesses and compositions and beam filtrations.     

Optical transillumination spectroscopy to quantify parenchymal tissue density: an indicator for breast cancer risk

Mammographic screening for early detection of breast cancer has proven valuable in improving breast cancer survival. However, breast cancer incidence is still increasing, and thus preventative oncology needs to receive more attention, with the goal of identifying women with increased risk of developing breast cancer in the future and offering them risk reduction interventions. Mammogram derived parenchymal density pattern has been shown by various authors to provide a high odds ratio for breast cancer. Near-infrared optical transillumination spectroscopy was employed to determine physiological properties of the breast tissue to quantify differences in women with low or high breast cancer risk. Specifically in this study, women who had a recent mammogram underwent examination of their breast tissue by optical transillumination spectroscopy. Areas of adipose and glandular tissues which give rise to mammographic density patterns also have characteristic optical transillumination spectra. Correlation between optical transillumination spectroscopy and mammographic density pattern was established using partial least squares analysis. Results show that predicted tissue density based on optical transillumination spectroscopy correlates with mammographic observed tissue density, with a Spearman Rank correlation coefficient of 0.72. This suggests that optical transillumination spectroscopy may be a promising tool to quantify and monitor changes in breast cancer risk.     

Quality assurance breast phantoms for screen-film mammography: design and use.

Used properly, well-designed breast phantoms are a very useful part of the mammography QA program. However, they should be designed specifically for the purpose. The principles involved are discussed and illustrated by the design of the unit shown in figure 1. QA phantoms also must be applied appropriately. Procedures are described for checking the consistency of film density, evaluating image quality, and checking phototimer operation. The simple film density measurement test (table 2) also provides a useful check on the constancy of patient dose levels. However, errors may result when QA phantoms are used for dosimetry, primarily because their composition differs from that of the mixture BR12, which is usually taken as the standard for dosimetry measurement. Procedures are described for computing average glandular dose, as well as measuring the two required quantities: the beam HVL and the exposure in air required for proper film density.     

Mammographic findings after breast cancer treatment with local excision and definitive irradiation

Following local excision and definitive irradiation of 163 breast cancers in 160 women, alterations in mammographic patterns were observed for up to 7 years. Skin thickening was observed in 96% of mammograms obtained within 1 year of completing therapy and was most pronounced in women treated with iridium implant, chemotherapy, or axillary dissection. In 76% of mammograms, alterations in the parenchymal pattern, including coarsening of stroma and increased breast density, were seen at 1 year. Neither skin nor parenchymal changes progressed after 1 year. Within 3 years of treatment the parenchymal density, which usually regressed, did not change in all patients. At 3 years skin thickness and the parenchymal pattern had returned to normal in less than 50% of the breasts of these women. Scars developed in approximately one-quarter of women. They were present on the initial post-treatment mammogram and remained unchanged on serial studies. Coarse, benign calcifications also developed in the breasts of about one-quarter of women. Microcalcifications developed in 11 breasts; biopsy specimens of six were benign. Benign microcalcifications may be related to therapy.     

Detection of incidental breast tumors by noncontrast spiral computed tomography of the chest

PURPOSE: The aim of this study was to investigate the frequency of breast tumors and breast cancers with noncontrast spiral chest computed tomography (CT). MATERIAL AND METHODS: A clinical study was conducted to evaluate findings in the mammary region of 1008 consecutive patients with no mammary symptoms or signs who underwent noncontrast spiral CT of the chest from April 2003 to March 2006. RESULTS: Six cases of breast abnormality were detected among the 1008 women. Three were primary breast cancers, one was metastatic breast cancer, and two were benign tumors. All four breast cancer patients were over 70 years old. The characteristics of the tumor margins on CT scans corresponded to the mammography and ultrasonography findings. The mammographic background density ranged from inhomogeneous high-density breast to fatty breast. The detection rate of primary breast cancer by noncontrast spiral CT was 0.30%. CONCLUSION: Noncontrast spiral chest CT occasionally detects nonsymptomatic breast cancers, especially in elderly patients.     

乳腺X线致密度与激素受体和人表皮生长因子受体2的相关性探讨

目的探讨乳腺X线致密度与乳腺癌中雌激素受体、孕激素受体及人表皮生长因子受体2之间是否具有相关性。方法回顾性收集了615例经手术证实的原发性乳腺癌患者。就诊时均行乳腺X线摄影,并根据美国放射学会制定的乳腺影像报告及数据系统(BI-RADS)对乳腺X线致密度进行分型。所有病例术后或穿刺后标本均行免疫组织化学染色检测雌激素受体、孕激素受体及人表皮生长因子受体2表达水平,并分析乳腺X线致密度与激素受体、HER2表达及年龄因素之间的相关性。结果乳腺X线致密度随年龄增长逐渐由高向低过渡(r=-0.529,P<0.001)。乳腺X线致密度与孕激素受体表达呈正相关(r=0.099,P=0.014<0.05),与雌激素受体(r=0.016,P=0.699>0.05)及人表皮生长因子受体2表达(r=0.077,P=0.057>0.05)未见明显相关性。结论乳腺X线致密度与乳腺癌孕激素受体表达呈正相关,与患者发病年龄呈负相关。